Individual pocketing hard, small stones (7)
I believe the answer is:
shingle
'stones' is the definition.
(shingle is made up of stones)
'individual pocketing hard small' is the wordplay.
'individual' becomes 'single'.
'pocketing' is an insertion indicator (pocket can mean to steal or take possession of).
'hard small' becomes 'h' (abbreviation used in pencil classifications; 'small' suggests a short form).
'single' placed around 'h' is 'SHINGLE'.
(Other definitions for shingle that I've seen before include "Loose stones" , "beach? Yes and no" , "Water-worn pebbles - roofing tile" , "may be lying on the beach" , "Bob" .)